Modified olefin polymers

ABSTRACT

Chemically modified olefin polymers are made by reacting solid particles of ethylenically unsaturated olefin polymer with an oxy-addition agent in a compatible non-solvent liquid. The liquid is one which wets the polymer but does not dissolve or soften it. The polymer is particularly polypropylene and especially substantially isotactic and thermoplastic unsaturated polypropylene. The oxy-addition agent is particularly an epoxidizing agent such as hydrogen peroxide or a percarboxylic acid. Useful modified polymers include epoxidized polyolefins which are more polar than the parent polyolefins and can be used as intermediates in making other derivatives such as diols, ethers and esters.

This invention relates to the manufacture of modified olefin polymers,in particular modified polypropylene polymers.

Polyolefins are a well known class of thermoplastic polymers of moderatestrength and toughness (as compared with modern so-called "engineeringpolymers") and good chemical resistance; their relative inertnessarising largely from their near paraffinic structures. Often thisinertness is an asset, for example in piping for gas, water etc., orwhen used in lining chemical reactors, but for some uses it can be adisadvantage. Thus, it is difficult to cross link the polymers toincrease strength, stiffness and temperature resistance, in a controlledmanner, or to modify the polymer surface to make it more receptive orreactive to dyestuffs.

One way of making such polymers more reactive so that cross-linking orsurface modification can be carried out in a controlled manner is tocopolymerise into the polymer a monomer that provides a site forsubsequent reaction. A significant part of this line of development hasbeen by way of the synthesis of polyolefins, particularly polypropylene,using commonomers that introduce unsaturation into the molecule, usuallyin side chains. Examples of syntheses that follow this approach includethose described in U.S. Pat. No. 4,606,077, European PublishedApplications Nos. 01710285 A and 0311299 A, PCT Application No. 90-12818A, Japanese published Applications Nos. 02-051512 A and 02-145611 A andthe article by G. Gechin and T. Simonazzi in Macromolecular Preprints1989.

The unsaturation in the polymer can be used as a site for furtherreaction, and, if it is the side chain that is unsaturated, or if theunsaturation is only at the end(s) of the polymer chain, the furtherreaction is unlikely to result in cleavage of the main chain. Cleavage,would reduce the molecular weight in an uncontrolled manner with acorresponding adverse effect on the physical, especially mechanical,properties of the polymer. However, the relatively insert nature ofolefin polymers makes such farther reaction awkward to carry out.Usually, in prior proposals, the polymer is dissolved, reacted insolution and the product subsequently isolated by evaporating thesolvent. Typically toluene or other similar potent solvent has beenused, if necessary, at elevated temperature to ensure solution of thepolymer. Such methods are satisfactory in small scale laboratorypreparations but are not suitable for large scale manufacture. Thepresent invention adopts a different approach to the further reaction inthat the reaction with the unsaturated polymer is carried out in aliquid medium which is compatible with but not a solvent for the polymer(or the modified polymer product). This makes separation of the liquidmedium from the reaction product much easier and more straight forwardthan when solvents are used.

Accordingly the present invention provides a method of making achemically modified olefin polymer which comprises dispersing solidparticles of an ethylenically unsaturated olefin polymer in a liquidmedium which is a compatible non-solvent for the unsaturated polymer;reacting the unsaturated polymer with an oxy-addition agent,particularly one which does not leave significant reactive residues andespecially an epoxidising agent, in the liquid medium; and recoveringthe chemically modified polymer.

The polymers used as starting materials in this invention areunsaturated polyolefins. As the unsaturation is used to introducefunctionality into the polymer rather than being itself the source ofdesired properties (as in diene rubbers) the bulk of the units in theunsaturated polyolefin are derived from mono-olefins which are usuallyalpha-olefins typically having from 2 to 10 carbon atoms. Where thepredominant alpha-olefin units are derived from monomers other thanethylene, the polymer is desirably substantially isotactic. Isotacticolefin polymers are typically thermoplastic and this invention isparticularly directed to the production of chemically modifiedthermo-plastic olefin polymers. In particular, the invention isapplicable to the manufacture of chemically modified polypropylene,especially substantially isotactic and thermoplastic polypropylene, andcorrespondingly the starting material for such modified polypropylene isan unsaturated polypropylene. This invention particularly includes amethod of making a chemically modified polypropylene which comprisesdispersing solid particles of an ethylenically unsaturated, particularlya substantially isotactic and thermoplastic, poly-propylene in a liquidmedium which is a compatible non-solvent for the unsaturatedpolypropylene: reacting the unsaturated polypropylene with anoxy-addition agent, particularly one which does not leave significantreactive residues and especially an epoxidising agent in the liquidmedium; and recovering the chemically modified polypropylene.

In the unsaturated olefin polymer, it is particularly desirable that theunsaturation does not lie in the main polymer chain remote from the endsof the chain. As is noted above, attempts at modification of suchpolymers can readily lead to chain cleavage. Thus, if the monomers usedto synthesise the unsaturated polymer include significant amounts ofconjugated di- or higher olefins such as 1,4-butadiene care may beneeded to avoid generating polymers with unsaturation in the polymerchain. One particularly useful way to introduce unsaturation into thepolymer is to copolymerize the olefin monomer(s) with a diene (polyene)having one alpha-olefinic double bond and having one (or more) otherdouble bond(s) (desirably not conjugated with the alpha-olefin doublebond) which does not polymerised under the olefin polymerisationconditions used (see below). Typically the carbon atoms of the otherdouble bond(s) is (are) bound to 3 or 4 further carbon atoms vis:##STR1## Examples of such unsaturated polymers and their synthesis aredescribed in Japanese published Applications Nos. 02-051512 A and02-145611 A and PCT application No WO 91/18030 (PCT/GB91/00762). Thesepolymers have unsaturation randomly (statistically) distributed alongthe polymer chain but situated in side chains. Another way to synthesiseunsaturated polymers, especially polypropylene, is to conduct thepolymerisation using a catalyst that generates unsaturation at the endof the polymer chain during chain transfer. For Example, isotacticpolypropylene synthesised using a stereorigid zirconocene and alkylaluminoxane catalyst system in a bulk (liquid propylene) polymerisationcan have terminal unsaturation as a result of beta-hydride eliminationin chain transfer. This general type of polymer is described by R.Mulhaupt and T. Dushek, Preprint from III European Federation Symposiumon Polymeric materials, Sorrento, Oct. 1st to 5to 1990.

The unsaturated olefin polymer will, typically, have a minimumunsaturation of 0.025 mmol (C═C).(g polymer)⁻¹ as lower levels ofunsaturation do not generally give, after reaction, modified productshaving properties significantly different from those of unmodified orsaturated (but otherwise equivalent) olefin polymers. This levelcorresponds to a (calculated) Iodine No. of about 6 [mg I₂.(g polymer)⁻¹]. Where the unsaturation is introduced into a polypropylene chain bycopolymerising propylene with an alpha-olefin/other olefin diene, suchdienes typically have molecular weights (as monomers) of about 125, andfor such monomers this lower limit corresponds to a level of about 0.1mole % of diene monomer units in the polypropylene. More usually theunsaturation will be at least 0.12 mmol (C═C).(g polymer)⁻¹ (Iodine No.about 30). The level of unsaturation will not normally exceed about 4,and not usually 3, mmol (C═C).(g polymer)⁻¹ (Iodine No. about 1000) assuch polymers tend to give products with excessive modification.Particularly useful levels of unsaturation are in the range 0.02 to 2.5,especially 0.1 to 1, mmol (C═C).(g polymer)⁻¹.

To maximise contact between the unsaturated olefin polymer and theoxy-addition agent in the liquid medium it is desirable that the polymerhas a high specific surface area. This can be obtained either by theunsaturated polymer having small particles or being porous with poreslarge enough to admit the liquid medium. Typically, the effectivesurface area will be at least 0.5 m².g⁻¹ and more usually at least 1m².g⁻¹. Unsaturated polypropylene having unsaturation in side chainsmade by copolymerising propylene and a suitable diene (see above), in agas phase, bulk (liquid propylene) or diluent process using conventionalhigh stereospecificity titanium (IV) catalysts on MgCl₂ supports are, asex-reactor materials, typically porous particles having an overallaverage size (calculated as the diameter of spheres of volume equal tothe particle volume) of about 0.3 to 2 mm and a porosity of 5 to 30% byvolume giving an effective specific surface area of 5 to 15 m².g⁻¹.Similarly, unsaturated polypropylene, having chain terminal unsaturationmade by a process including hydride eliminating chain transfer, (seeabove), typically takes the ex-reactor form of a very fine powder e.g.having an average particle size of about 1 μm having a specific surfacearea of about 5 to 10 m².g⁻¹. Such materials can be readily reactedaccording to the invention.

The liquid medium used in the reaction with the unsaturated olefinpolymer is a compatible non-solvent for the polymer. A compatible mediumis one which thoroughly wets the polymer and, where the polymer isporous, penetrates the pores, under the conditions of the reaction. Theliquid medium is a non-solvent for the unsaturated polymer in that itdoes not dissolve the polymer nor substantially soften it although itmay cause the polymer particles to swell. Any swelling of the polymer bythe liquid medium will be less than that which causes the polymerparticles to disintegrate or soften to such an extent that theyagglomerate. In other words cohesion of the polymer particles is notsignificantly impaired and adhesion of the polymer particles is notsignificantly promoted by the liquid medium. The specific choice ofliquid medium will depend on the particular unsaturated olefin used, butit will be chosen from compatible non-solvents and will typically be anorganic liquid (under reaction conditions) such as an aliphatichydrocarbon, particularly an alkane; a halogenated aliphatichydrocarbon, particularly a halo-alkane; a carboxylic acid; a ketone; analcohol; an aromatic hydrocarbon, particularly an alkylbenzene; andmixtures of or containing such liquids. Relatively reactive liquids suchas ketones and alcohols can react with the epoxy forming reagent or themodified polymer, typically to generate by products which may beundesired, if only by loss of the liquid reagent or modified polymer,and thus if used will be used with caution. Aromatic liquids such astoluene and the xylenes tend to be fairly good solvents for polyolefins,particularly polypropylenes, and if used, will be used under conditionswhere they are non-solvents for the polymer, typically by keeping thetemperature at about or even below ambient temperature. Alkylbenzeneswith longer alkyl side chains tend to be less good solvents for thepolymers and it may be possible to use them at higher temperatures. Themore useful liquids are among the aliphatic and halogenated aliphatichydrocarbons and carboxylic acids. We have found that liquid alkanessuch as n-heptane, chlorinate alkanes such as chloroform and carboxylicacids such as acetic acid can be used as the liquid reaction medium.Halogenated liquids such as chloroform may cause the polymer to swell,but in our experience this does not go so far as to excessively softenthe polymer so as to approach dissolving it.

The medium can include other liquids, which do not themselves wet thepolymer, in admixture with a compatible liquid provided that the mixtureor a component of the mixture does wet the unsaturated polymer to enableefficient reaction with the epoxy forming reagent. The most usual suchother liquid will be water either, where it is miscible, mixed with thecompatible liquid e.g. acetic acid, or, where it is immiscible, as aseparate phase e.g. as with chloroform or liquid alkanes.

The oxy-addition agent is an oxidising agent which adds an oxygencontaining substituent to either or both the double bonded carbon atomswhist converting the double bond into a single bond without leavingreactive residues at the end of the reaction. Thus, the oxy-additionagent does not cause substantial cleavage of the double bond or of themain polymer chain. Most usually the reaction yields either an epoxideor hydroxyl substituted product groups. A convenient way of visualisingthe reaction of the oxy-addition agent with the double bond system is asfollows: ##STR2## where X is a hydroxyl group;

Y is a halogen, particularly chlorine atom or a group OR where

R is a hydrogen atom, or an ether or ester residue (i.e. R is alkyl,aryl or C(O)R' where R' is alkyl or aryl [as defined for R]); or

X and Y together are --O-- (thus giving an epoxide group). Suitableoxy-addition agents include epoxidising agents, discussed further below,diol forming oxidising reagents, such as peroxides and hydroperoxides(which can yield the diols themselves or corresponding ether or esterwith an organic residue of the reagent) or systems generating singletoxygen species, such as aqueous hydrogen peroxide, bromine and base, andinorganic oxidising agents such as hypohalite, particularly aqueoushypochlorite. The avoidance of reactive residues at the end of thereaction effectively excludes heavy metal oxidising agents such aspermanganate. Such reagents tend to leave metal oxide residues whichdiscolour or otherwise contaminate the product and are difficult toremove. Often these residues are themselves oxidants or pro-oxidantmaterials as with permanganate which leaves residual manganese dioxide.Such residues adversely affect the stability of products formed from themodified polymers and may interfere with subsequent desired reactions.

As is mentioned above, epoxidising agents are particularly desirableoxy-addition agents in the invention. Epoxidising agents areoxy-addition agents which can convert ethylenic double bonds in theunsaturated olefin polymer into epoxide groups. The most important groupof epoxidising agents are peroxy compounds including hydrogen peroxideand, particularly, percarboxylic acids and their salts. Examples includeperalkanoic acids e.g. peracetic acid, peraromatic acids e.g.m-chloroperbenzoic acid (MCPBA) and salts of such acids e.g.monomagnesium peroxyphthalate (MMPP). Percarboxylic acids areparticularly useful epoxidising agents because they can yield a highyield of epoxide groups with only slight (and possible no) formation ofby products. Other peroxy compounds, including hydrogen peroxide, aregenerally less specific and typically give rise to by products such asdiol groups, which are probably formed by ring opening of epoxidegroups, methylene groups believed to be formed by dehydration of a diolOH group and an adjacent methyl group, or other derived products such asethers or esters which can be formed by reaction of epoxy groups withalcohols or carboxylic acids present in the reaction medium, for examplein or as the compatible non-solvent. The non-specific epoxidising agentscan be considered as diol forming agents referred to above.

Although percarboxylic acids are available as pure compounds, they aremore easily handled as, and `commercial` grade materials are usually, amixture with or a solution in the corresponding carboxylic acid oftenalso mixed with water and/or mineral acid and/or hydrogen peroxide.Where the corresponding carboxylic acid can be a compatible non-solventfor the polymer, the `commercial` grade percarboxylic acid can act asits own reaction medium. In practice the epoxidising agent and thecompatible non-solvent will be chosen so that the epoxidising agent issufficiently soluble to facilitate reaction with the unsaturatedpolymer.

The amount of epoxidising agent used will normally be at leaststoichiometrically equivalent to the double bonds to be reacted in thepolymer and typically a convenient excess will be used to speed thereaction. We have not found it necessary to use more than twice thestoichiometric requirement and have obtained best results using amountsin the range 105 to 130% of the stoichiometric requirement.

The reaction between the unsaturated olefin polymer and theepoxy-forming reagent proceeds over a wide range of temperatures. Webelieve that the limits are set primarily by the freezing and boilingpoints of the liquid medium (or possibly by the melting point of thepolymer) other than the reaction itself. Generally the temperature willbe within the range -50° C. to 100° C. more usually at least ambienttemperature (about 20° C.) and particularly 40° to 90° C. Generally, thereaction runs more quickly at higher temperatures but highertemperatures may encourage further reaction of epoxide groups and/orlead to crosslinking of the polymer.

Where the oxidising agent used is an epoxidising agent, we believe thatthe initial reaction in the invention is the conversion of ethylenicdouble bonds in the unsaturated olefin polymer into epoxide groups:##STR3## The initially formed epoxide can react with a variety ofmaterials which may be present in the reaction mixture to givehydroxylic and/or ether and/or ester group containing materials:##STR4## where R is an alkyl or aryl group. Further where the doublebond has an adjacent methyl group, the following sequence generating a3-hydroxyprop-1-enyl group may occur: ##STR5## Where the epoxide groupin the polymer is specifically desired, as for example the reactive sitefor a specific further reaction, then these side reactions are undesiredbecause they remove epoxide groups from the polymer. In many cases,however, the purpose of epoxidising the polymer is to introduce polargroups into the polymer, the hydroxyl, oxyether or acyl groupsintroduced by the `side` reactions may be the same as or equivalent todesired groupings from epoxide ring opening reactions. In such cases theside reactions may not be disadvantageous.

A variety of subsequent reactions with epoxide groups in the modifiedpolymers produced in this invention is possible. As well as thereactions identified above as `side` reactions but conducteddeliberately, the following outline schemes illustrate thepossibilities. ##STR6## Of these, a and b illustrate graftpolymerisation and c the introduction of a reactive double bond thatcould be used to cross link the polymer.

Similar reactions are possible with modified polymers including groupssuch as: ##STR7## where R is alkyl or aryl, which are generated fromepoxy groups or made directly in the reaction between the oxy-additionagent and the unsaturated olefin polymer. Generally, the reactions withthese species run more slowly than with epoxy groups.

The process of the invention can be used to make polymer which, on theirown or blended with other polymer, especially with unmodifiedpolyolefins or polyesters, particularly the materials generated byreaction sequence a) above, have a variety of practically usefulproperties. The introduction of polar, particularly hydrophilic groups,into the polymer can enhance the receptivity towards dyestuffs, withapplications in films and fibres, towards paints and inks, especiallyprinting inks, with applications in films such as packaging films, andsurface coatings, as compatibilisers in blends, particularly by graftingsuitable oligomeric units onto the olefin polymer using the epoxidefunction, as in blends of polyolefins and polyesters compatibilised withmaterials generated by reaction sequence a) above, to produce polymerswith novel or exotic rheological properties, and, in the form or porousparticles, as the basis for interpenetrating network microstructureslinked through the epoxide function.

The following Examples illustrate the invention. All parts andpercentages are by weight unless otherwise stated.

Materials and Abbreviations

MOCD--7-methyl-1,6-octadiene (from Shell Chemicals Limited) hydrogenperoxide (H₂ O₂) aqueous solution containing 30% H₂ O₂ (about 9.7M H₂O₂)

AcOOH--reagent grade material containing about 30% peracetic acid, about30% acetic acid, 3% hydrogen peroxide, 2% sulphuric acid remainder(about 33%) water (about 4.4M peracid and 6M total peroxide). Availablefrom Aldrich or Interox.

n-AcOOH--AcOOH with the sulphuric acid neutralised by the addition ofsodium hydroxide (pH ca 4).

m-CPBA--reagent grade m-chloroperbenzoic acid containing 55 to 60%peracid (molar amounts quoted are approximated based on 57.5% peracid).

MMPP--reagent grade monomagnesium peroxyphthalate hexahydrate (nominally100% material).

AcOH--glacial acetic acid

IPA--isopropyl alcohol

EC 180--is an aliphatic hydrocarbon diluent consisting essentially ofdodecane isomers and having a boiling point in the range 170° to 180° C.It is used from a stock stored under dry nitrogen sparging to keep itfree from water and oxygen.

Analysis and Test methods

The degree of unsaturation of propylene/MOCD copolymers was calculatedfrom ¹ H nmr analysis of the copolymer (in solution). The integration of-CH═C< protons as a proportion of that of other aliphatic protons,together with knowledge of the structure of the monomers (in particularthe number of hydrogen atoms they contain) permits the calculation ofthe proportion of diene monomer derived units in the copolymer (forbinary polymers). The degree of unsaturation is quoted as mole % MOCDresidues or as mmol double bond per gram of polymer.

¹ H nmr was carried out on polymer samples dissolved in TCE at 100° C.on a GSX 400 nmr spectrometer at 400 MHz using TMS as internal standard.Quantitative data were calculated by a similar method to the `degree ofunsaturation` calculations (see above) but using the appropriate nmrpeaks. Results are quoted as mol % of MOCD derived residues containingthe identified groups.

IR was carried out on 40 to 80 μm thick film samples pressed frompolymer powder, on a Perkin Elmer 1600 series FTIR spectrometer.Quantitative data for epoxide groups were obtained from a peak at about1125 cm⁻¹ by normalising the spectra of epoxidised and non-epoxidisedpolymers to match peaks common to both spectra so far as possible. Thepeak height of the `epoxide` peak (at about 1125 cm⁻¹) was taken as apercentage (in transmission mode). This value corresponded to about 1.5times the value of mole % epoxide obtained from measurements on epoxideprotons by nmr. The result obtained from IR measurements is quoted as`mole % epoxide(IR)` (without normalisation against the nmr figure).

Melt Flow Index (MFI) was measured according to ASTM-D 1328-N (using the190/10 scale). Results are quoted in g. (10 min)⁻¹.

Melting Point (m.p.) was measured on a hot stage microscope with themelting point judged by eye. Results are quoted in °C.

Crosslinking was assessed as insolubles in a hydrocarbon solvent(EC180--a C₁₂ alkane fraction). About 3 g of polymer was stirred withEC180 at 130° C. to dissolve the bulk of the polymer. The remainingsolid was separated in a warmed glass sinter which was then extractedfor 6 hours in a soxhlet apparatus using boiling EC180 as the solvent.The degree of crosslinking is assessed as the weight % of the polymerremaining undissolved.

Flexural Modulus (FM) was measured according to ISO 178. Results arequoted in GPa.

Dye Pen test Samples of film pressed as for IR spectra were marked witha `Politest` dye test pen (from Lorilleux International of Spain) andthe marked film was visually assessed on a ranking scale A to E (A--mostdye adhered, E--least dye adhered).

Foil Stick test During preparation of plaque samples for FM testing thepolymer was pressed into a plaque against aluminium foil liners. Thedifficulty of removing the foil from the plaque was assessedqualitatively with the results expressed as a ranking order (among thesamples tested) lowest rank indicating most sticking.

Synthesis of polymers Propylene/MOCD copolymers

These copolymers were made by the method described below (the method ofExample SE5 in our PCT Application No. PCT/GB91/00762). The unsaturatedcopolymers of propylene and MOCD were made using a diluentpolymerisation technique in a pilot scale autoclave reactor.

This reactor is a nominal 5 liter stainless steel pilot scale autoclavehaving a heating jacket operated to control the temperature of thecontents of the autoclave. The reactor is fitted with a mechanicalstirrer, temperature and pressure sensors, vacuum, nitrogen and hydrogengas and propylene gas, supply lines and a valved port to enable theaddition of other reaction components. In operation the autoclave isthoroughly dried, sealed and purged with nitrogen. The hydrocarbondiluent, diene monomer, prepolymerised catalyst, aluminium triethylco-catalyst and silane are introduced through the valved port and thevalve closed. The stirrer is started and propylene is added and thepropylene line is then closed. Gaseous hydrogen is supplied to thereactor to give a pre-determined hydrogen partial pressure at the startof polymerisation. At the end of the polymerisation, the reactor isvented to reduce the pressure to ambient and the autoclave is unsealedto recover the polymer.

The catalyst used is a slurry of a conventional magnesium chloridesupported titanium, high stereospecificity Ziegler-Natta olefinpolymerisation catalyst made as follows. Solid magnesium chloride istreated with ethanol to give a haloethanolate (probably magnesiumchloride with ethanol of crystallisation) which is dispersed in hotEC180 and spray quenched into cold EC180. The magnesium haloethanolateslurry is treated with TiCl₄ (about 6 g per g of the magnesium haloethanolate) and heated to 110°-120° C. Di-isobutylphthalate is added asinternal electron donor (about 14 g per g of the magnesiumhaloethanolate). The mixture is allowed to settle and the supernatantliquid is discarded. The treatment with TiCl₄ is repeated at ca. 110° C.and excess TiCl₄ is then removed by repeated dilution, settling anddecanting. Before use in the Examples, the catalyst is prepolymerised(with propylene) using aluminium triethyl as co-catalyst and di(loweralkyl) dimethoxy silane as external electron donor at approximate molarratios of Al:Ti:Si of 3:1:1. The prepolymerisation is stunned with CO₂when about 3 g polypropylene per g catalyst has been made.

This method can be used to produce unsaturated copolymers having a rangeof degree of unsaturation by varying the proportion of MOCD monomerincluded in the reactor. The polymer is recovered as particles having atypical average diameter of about 1 mm, a porosity of about 25% byvolume and a specific surface area of about 7 g.m⁻².

Terminally unsaturated polypropylene

This polymer was produced as follows: 1,2-di(tetrahydroindenyl)ethylenezirconium chloride in solution in toluene (1 ml; 1 mg(catalyst).ml⁻¹(solution) was mixed with methyl aluminoxane dissolved in toluene (15 mlof 4.4M solution) and added to a stirred autoclave (3 l nominal volume)which had been thoroughly flushed with gaseous propylene at ambientpressure. Liquid propylene (3 l) was then added and the autoclave heatedto 65° C. and the reaction allowed to proceed under the autogenouspressure for 90 minutes. The remaining propylene was then slowlyevaporated off. The product was recovered to yield 364 g of polymer as afine powder having a particle size of about 1 μm. This polymer had amolecular weight of about 6 kD and a degree of unsaturation of about0.17 mmol (C═C).(g polymer)⁻¹ (iodine No about 42) and a specificsurface area of about 7 g.m.⁻².

EXAMPLE 1

m-CPBA (1 g; ca 3.3 mmol) was dissolved in chloroform (25 ml).Propylene/MOCD copolymer powder, having a degree of unsaturation of 7.3mol % MOCD residues, corresponding about 1.8 mmol double bond. (gpolymer)⁻¹, (2 g; about 3.6 mmol double bond) was dispersed in thechloroform solution and left to stand at ambient temperature (ca 20° C.)for about 16 hours. The polymer product was washed thoroughly withacetone to remove the chloroform and then vacuum dried at 60° C. for 2hours. ¹ H nmr analysis of the modified polymer product indicated thatit contained about 5.7 mol % epoxidised MOCD residue, equivalent toabout 1.4 mmol epoxide residues per gram of modified polymer product,and about 1.8 mol % unepoxidised MOCD residues. The infrared spectrum ofthe polymer product had peaks at 880, 1125 and 1248 cm⁻¹ absent from thespectrum of the starting copolymer.

EXAMPLE 2

Propylene/MOCD copolymer powder, having a degree of unsaturation of 2mol % MOCD residues, corresponding to 0.48 mmol double bond. (gpolymer)⁻¹, (20 g; about 9.6 mmol double bond) was slurried inchloroform (100 ml) with stirring. m-CPBA (3.33 g; ca 11 mmol) was addedover a period of 45 minutes at ambient temperature, the slurry wasstirred for a further 21/2 hours, allowed to stand for about 16 hoursand then thoroughly washed with acetone and dried. ¹ H nmr analysisindicated that the modified polymer product contained 1.5 mol %epoxidised MOCD residues, about 0.36 mmol(epoxide residues). (gproduct). The IR spectrum of the modified polymer product had a peak at1122 cm⁻¹ not present in the spectrum of the starting material.

EXAMPLE 3

Sodium hydroxide (1 g) was added to stirred AcOOH (50 ml; about 2230mmol peracid; about 300 mmol total peroxy group) at 0° C. and stirringwas continued until the sodium hydroxide dissolved (about 11/2 hours).Propylene/MOCD copolymer powder, having a degree of unsaturation of 7.3mol % MOCD residue, corresponding to about 1.8 mmol double bond. (gpolymer)⁻¹, (5 g; 9 mmol double bond) was added, the mixture was stirredfor 1 hour and the modified polymer product was isolated washed withacetone and dried in a vacuum oven at 60° C. for about 16 hours. ¹ H nmranalysis of the modified polymer product indicated that it contained 1.7mol % epoxidised MOCD residues, about 0.4 mmol epoxide (g product), and(calculated as mol % modified MOCD residues) 1.3 mol % C═CH₂ groups,believed to be generated by dehydration of initially formed diol groups,2.7 mol % CHOR (where R is H or acetyl) groups, believed to be generatedby ring opening reactions of epoxide groups, and 1.9 mol % unmodifiedMOCD residues. The IR spectrum of the modified polymer product had apeak at 1125 cm⁻¹ not present in the starting material and a peak at1671 cm⁻¹ in the starting material was not apparent in the modifiedpolymer product.

EXAMPLE 4

Terminally unsaturated polypropylene powder, having a number averagemolecular weight of about 6 kD giving about 0.1 mmol double bond, (gpolymer)⁻¹, (50 g; 8 mmol double bond) was slurried in chloroform (100ml). m-CPBA (5 g; 17 mmol) was added and the mixture was stirred atambient temperature for 1 hour. The modified polymer was isolated,washed with acetone and dried. Before spectroscopic analysis themodified polymer was purified by dissolving it in hot toluenereprecipitating by cooling separating and drying. ¹ H nmr analysis ofthe purified modified polymer product indicated that it containedepoxide groups and unreacted double bonds together with ring openedproducts from epoxy groups and methylene groups although theconcentration of these in the polymer is not great enough to quantify bynmr (c.f. the degree of unsaturation of the starting polymer). The IRspectrum of the reprecipitated polymer had a peak at 1166 cm⁻¹ notpresent in the spectrum of the starting material.

EXAMPLE 5

A matrix experiment including a number of runs was conducted. Thefollowing general procedure was used.

Propylene/MOCD copolymer powder, having a degree of unsaturation of 1.5mol % MOCD residues, corresponding to about 0.34 mmol double bond. (gpolymer)⁻¹, was dispersed with stirring in the liquid reaction medium(compatible non solvent) (100 ml) and the temperature adjusted (ifnecessary) to the desired reaction temperature. The epoxy formingreagent (in solution in a suitable solvent if necessary) was addedgradually to the reaction mixture over a period of about 1 hour. Samplesof the polymer were removed from the reaction mix at (various)intervals, washed thoroughly with acetone and then water/IPA mixture(75:25 by volume) and dried in a vacuum oven at 50° C. for 2 hours. Atthe end of the reaction time the remaining modified polymer was isolatedand similarly washed and dried.

Information on the materials used and the reaction conditions is givenin Table 1 below. In Runs 5, 8 to 13, 16 and 17, the reaction media weremixtures in the volume ratios given in Table 1. In runs 10 to 12 theepoxidising agents were solids used as solutions; m-CFBA (Runs 11 and12) was dissolved in chloroform (6 g solid in 50 ml solvent) and the pHof the aqueous reaction phase was buffered to 4.5 to 5 by adding 1Maqueous NaOH as necessary; MMPP (run 10) was dissolved in water (50 gsolid in 250 ml water) and the pH was adjusted to 5.0 using sodiumhydroxide before use.

The modified polymer samples were analysed spectroscopically for epoxidegroup content, unmodified MOCD residues and other groups i.e. byproducts presumed to be from reactions including epoxide ring opening,and for crosslinking (by solubility) and the results are set out inTable 2 below.

Samples were further tested for MFI, melting point, flexural modulus andthe dye pen and foil stick tests. The results are set out in Table 3below.

                                      TABLE 1                                     __________________________________________________________________________    Epoxy Reagent            Mix      Reaction                                    Run          mmol                                                                              Reaction                                                                              Ratio                                                                              Temp                                                                              Time                                        No  matl.                                                                              qty.                                                                              perox.                                                                            Medium  (by vol)                                                                           (°C.)                                                                      (min)                                       __________________________________________________________________________     1  H.sub.2 O.sub.2                                                                     5 ml                                                                             48.5                                                                              AcOH    --   25   90                                          2  H.sub.2 O.sub.2                                                                     5 ml                                                                             48.5                                                                              AcOH    --   80   30                                          3  AcOH  5 ml                                                                             23.5                                                                              CHCl.sub.3                                                                            --   50  1000                                         4  AcOH  5 ml                                                                             23.5                                                                              CHCl.sub.3                                                                            --   -40 1000                                         5  AcOH  5 ml                                                                             23.5                                                                              H.sub.2 O/CHCl.sub.3                                                                  90:10                                                                              24  360                                          6  AcOH  5 ml                                                                             23.5                                                                              hexane  --    4  360                                          7  AcOH  5 ml                                                                             23.5                                                                              hexane  --   50  120                                          8  n-AcOH                                                                              5 ml                                                                             23.5                                                                              H.sub.2 O/CHCl.sub.3                                                                  90:10                                                                              50  240                                          9  n-AcOH                                                                              5 ml                                                                             23.5                                                                              H.sub.2 O/CHCl.sub.3                                                                  90:10                                                                               4  300                                         10  MMPP 50 g                                                                              200 H.sub.2 O/IPA                                                                         75:25                                                                              50  1000                                        11  m-CPBA                                                                              6 g                                                                              20  H.sub.2 O/CHCl.sub.3                                                                  80:20                                                                              25  300                                         12  m-CPBA                                                                              6 g                                                                              20  H.sub.2 O/CHCl.sub.3                                                                  80:20                                                                              50  330                                         13  AcOH  5 ml                                                                             23.5                                                                              H.sub.2 O/                                                                            75:25                                                                              50  1000                                                         heptane                                                      14  AcOH  5 ml                                                                             23.5                                                                              heptane --   50  1000                                        15  n-AcOH                                                                              5 ml                                                                             23.5                                                                              hexane  --   50  120                                         16  AcOH  5 ml                                                                             23.5                                                                              H.sub.2 O/                                                                            60:40                                                                              50  200                                                          hexane                                                       17  n-AcOH                                                                              5 ml                                                                             23.5                                                                              H.sub.2 O/                                                                            40:60                                                                              50  255                                                          hexane                                                       __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                              Sample   Epoxide  MOCD   Other   Cross                                  Run   Time     (IR)     (nmr)  (nmr)   Linking                                No    (min)    (mol %)  (mol %)                                                                              (mol %) (wt %)                                 ______________________________________                                        1     90       0        2.3    0.1     4.5                                    2     15       0        2.2    0.5     11.3                                         30       0        1.4    0.7     12.8                                   3     50       0.5      1.1    1.1     12                                           1000     0        0      2.2     58.4                                   4     180      0.1      1.8    1.2     --                                           1000     2.2      --     --      5.6                                    5     60       0.5      --     --      --                                           180      0        1.2    1.1     --                                           360      0.6      --     --      1.3                                    6     60       0        2.3    0.4     --                                           180      0.1      1.8    1.3     --                                           360      0.6      1.6    1.5     0.3                                    7     30       0.5      --     --      --                                           60       1.7      --     --      --                                           120      2        0      1.1     0                                      8     30       0.4      1.8    0.9     --                                           60       0.7      1.5    0.9     --                                           240      1.5      0.5    1.8     0                                      9     300      0        1.5    1.3     0                                      10    1000     0        2.4    0.1     0                                      11    60       0.8      1.4    0.9     --                                           120      1.3      0.8    1.4     --                                           300      1.5      0.9    0.9     0                                      12    330      0.8      --     --      --                                     13    25       0        --     --      --                                           50       0.1      --     --      --                                           100      0.6      --     --      --                                           1000     1.2      --     --      --                                     14    15       2.4      --     --      --                                           70       2.7      --     --      --                                           1000     2        --     --      --                                     15    30       0.8      --     --      --                                           60       1.8      --     --      --                                           120      1.8      --     --      --                                     16    30       0        --     --      --                                           60       0.2      --     --      --                                           120      1        --     --      --                                     17    255      --       --     --      --                                     ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                              Sample                                                                  Run   Time     MFI      m.p.  FM     Dye   Foil                               No    (min)    (g.min.sup.-1)                                                                         (°C.)                                                                        (GPa)  Pen   Stick                              ______________________________________                                        1      90      48       175   0.99   D     2                                  2      30      29.5     180   1      D     3                                  3     1000     2.8      185   0.58   B     11                                 4     1000     58       175   1.1    C     5                                  5     360      84.5     145   1.06   C     7                                  6     360      85.5     145   1.05   C     6                                  7     120      91       140   1.06   B     10                                 8     240      93       140   1.06   C     9                                  9     300      91       140   1.04   C     8                                  10    1000     86.5     145   1.04   D     1                                  11    300      117      145   1.1    D     4                                  12    330      83.2     --    --     C/D   --                                 13    1000     90.3     --    --     C     --                                 14    1000     91.7     --    --     B     --                                 15     30      90.3     --    --     C     --                                        60      93.4     --    --     C     --                                       120      94.5     --    --     B     --                                 16    200      92.4     --    --     B     --                                 17    255      89.4     --    --     --    --                                 ______________________________________                                    

I claim:
 1. A method of making a chemically modified olefin polymerwhich comprises dispersing solid particles of an ethylenicallyunsaturated olefin polymer in a liquid medium which is a compatiblenon-solvent for the unsaturated polymer; reacting the unsaturatedpolymer with an oxy-addition agent in the liquid medium; and recoveringthe chemically modified polymer.
 2. A method as claimed in claim 1wherein the oxy-addition agent is an epoxidising agent.
 3. A method asclaimed in claim 2 wherein the epoxidising agent is hydrogen peroxide, apercarboxylic acid or a mixture of these.
 4. A method as claimed inclaim 1 wherein the ethylenically unsaturated olefin polymer issubstantially isotactic and thermoplastic unsaturated polypropylene. 5.A method as claimed in claim 1 wherein the ethylenically unsaturatedolefin polymer has a level of unsaturation of from 0.025 to 3mmol(C═C).(g polymer)⁻¹.
 6. A method as claimed in claim 5 wherein theethylenically unsaturated olefin polymer has a level of unsaturation offrom 0.1 to 1 mmol(C═C).(g polymer)⁻¹.
 7. A method as claimed in claim 1wherein the ethylenically unsaturated olefin polymer has a specificsurface area of at least 1 m².g⁻¹.
 8. A method as claimed in claim 1wherein the liquid medium is a compatible non-solvent selected fromaliphatic hydrocarbons; halogenated aliphatic hydrocarbons; carboxylicacids; ketones; alcohols; aromatic hydrocarbons; and mixtures of orcontaining such liquids.
 9. A method as claimed in claim 1 wherein theliquid medium is a compatible non-solvent selected from alkanes;halo-alkanes; alkylbenzenes; and mixtures of or containing such liquids.10. A method of making a chemically modified polypropylene whichcomprises dispersing solid particles of a substantially isotactic andthermoplastic, ethylenically unsaturated polypropylene in a liquidmedium which is a compatible non-solvent for the unsaturatedpolypropylene; reacting the unsaturated polypropylene with anepoxidising agent in the liquid medium; and recovering the chemicallymodified polypropylene.